*{
    padding: 0px;
    margin:0px;
}

body,html,.page,#root{
    width:100%;
    height:100%;
}

.box{
    width: 100%;
    height: 100%;
    position: relative;
    .mask{
        width: 300px;
        position: absolute;
        top: 50%;
        left: 50%;
        z-index: 999;
        transform: translate(-50%, -50%);
    }
}